Definition
This idiom is used to emphasize the uncertainty of events; many things can go wrong before something is completed.
功虧一簣
They thought victory was assured, but there's many a slip twixt cup and lip; they lost the competition in the end.
他們以為勝利在握，但世事難料，最終他們輸掉了比賽。
I thought the deal was done, but there's many a slip twixt cup and lip, so I am still waiting for final confirmation.
我以為交易已經完成，但世事難料，所以我還在等待最終確認。
She was so close to getting the job, but there's many a slip twixt cup and lip, so she must ensure she is fully prepared.
她差點就得到了那份工作，但世事難料，所以她必須確保自己完全準備好。